Question about Graphics Card

I'm thinking about buying an XFX ATi Radeon HD 5770 card but my computer only has a 300 watt power supply would i need to upgrade that too?

And if i do need to upgrade, what size and model would you prefer.

I would reccomend a 550W for a 5770.. heres one that I have and love it..

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341022&Tpk=550w%20fatal1ty

solid one though i find ocz to be wierd looking psu's .. just an opinion though still would eat off my pc power & cooling silencer though :P